Members djerickson Posted May 7, 2013 Members Share Posted May 7, 2013 I was the DJ at a Prom Saturday night for about 200 kids running V1 Mackie 450's over JBL PRX618XLF's. All's dialed in and sounding great. I'm running my faders at about 70% and the attenuators on the Mackie's and JBL's at about 11 o'clock. After 2 hours of the 4 hour gig, I suddenly lose my left channel! First thought is a problem with the Mackie 450 on that side. From my position it only takes me a few seconds to get to the speakers and I notice the signal input on the Mackie is flashing on and off randomly and at a rate not associated with the music playing. After a few more seconds the signal goes out all together and I realize the 618XLF sub on that side is also not putting out any sound. When I switch my attention to the sub I notice it's not registering a signal input and the power light has gone out.....D-E-A-D, dead! I quickly unpluged the cable feeding the sub and plug it into the Mackie (hit the bass roll-off switch) and my top is back up and running on that side. After 10 minutes and several attempts switching the JBL on and off the power light finally comes back on. I then ran a cable from the Mackie to the sub (I was hesitant to hook things back up the original way - mixer/sub/top - for fear the problem would reoccur and I didn't want to kill the sound on that side of the stage to do so. For the next 2 hours everything performed without incident. The whole thing happened so fast that I don't think anyone but me even new something had gone down. Needless to say it got my heart racing and I was glad the end of the night came without anymore excitment. If a sub does overheat and shuts down....doesn't it still pass the signal through?Up until the point of failure eveything was completely normal and I was running things at a fairly conservative level. Heat levels on the subs seemed in-line with what I had experienced before, very warm to not quite hot and the clip lights never even flashed, in fact I've only seen then flash a time or two in the six months I've owned them. (A side note - About a month ago I set up the same rig and upon intial power up, one of the subs wouldn't turn on! I assumed operator error and began checking all my power cords.....everything seemed in order and after doing nothing more than unplugging and plugging in the power cable....the same sub magically turned on.....and it was plugged in all the way the first time. Related to my current problem, I don't know...but I thought it worthy of mention.)This pair of JBL's was the biggest purchase of my audio life. I've run Behringer, Peavey, Yamaha, Turbosound, and B-52 speakers through a good handful of various Crown amplifiers without a single failure over 7 years and maybe 250 shows......to say I'm dissapointed this XLF died after a four months and 8 shows is putting it mildly!Since the sub seemed to perform fine before and after it's brief retirement.....am I looking at some sort of internal power supply problem? My first call tomorrow will be to JBL to begin the warranty repair process. How does that work....is it my dime to ship the sub to my nearest service center? I'm guessing they don't want me messing with removing and just shipping the amp. Anyone experienced this before? Sorry for being a bit lengthy and thanks in advance for all your help. Link to comment Share on other sites More sharing options...
Members JV90 Posted May 7, 2013 Members Share Posted May 7, 2013 Why are u running the attenuators at 11 o'clock? Is this the box that on 12 o'clock is mark a 0 dB? Altought I don't have the sub that you mention on your thread, but I have my sub's on another brand and I always adjust them at full 5 o clock, did you check your gains before the master fader? Link to comment Share on other sites More sharing options...
Members agedhorse Posted May 7, 2013 Members Share Posted May 7, 2013 One of the most common problems I have encountered is iec power connectors not fully inserted (even if you think so) and defective of just cheaply made iec connectors on the cord set. Your problem shares these symptoms. No. Signal will not pass via the high pass output to the tops in the event of power failure to the sub. Link to comment Share on other sites More sharing options...
Members djerickson Posted May 7, 2013 Author Members Share Posted May 7, 2013 Aged.....is your advice to wait and see if the sub fails again before seeking warranty service? Link to comment Share on other sites More sharing options...
Members Shaster Posted May 8, 2013 Members Share Posted May 8, 2013 I've also had a compressor with a faulty IEC receptacle. The compressor would cut in and out once or twice a gig. I thought it was a bad AC cable but it was actually the unit itself. Warranty repair and I was good to go. Not saying that's the issue here, but it could be worth a look - after you've checked and/or swapped out your IEC Cable. Link to comment Share on other sites More sharing options...
Members Vito Corleone Posted May 8, 2013 Members Share Posted May 8, 2013 I can only verify this: it only happened at a couple of different venues--where we were pretty much putting the whole band on a single circuit. It happened once when we were working with a proper sound engineer and he identified the cause as pulling too much off a single circuit. We've since taken extra care to make sure the FOH circuit is isolated and we haven't had the problem since. Link to comment Share on other sites More sharing options...
Members agedhorse Posted May 8, 2013 Members Share Posted May 8, 2013 Most class d amps have under voltage protection. Link to comment Share on other sites More sharing options...
Members Pro Sound Guy Posted May 8, 2013 Members Share Posted May 8, 2013 First thing that came to mind when I read your description was thermal.Cooled, and unit fired up.Could be anything but that was my thought. Link to comment Share on other sites More sharing options...
Members djerickson Posted May 11, 2013 Author Members Share Posted May 11, 2013 When a powered speaker thermals and shuts down to protect it's self from damage does it actually turn the amp off so it won't even pass a signal through or does it just limit the output to the speaker in the cabinet while it cools back down to a safe temperature? Link to comment Share on other sites More sharing options...
Members agedhorse Posted June 7, 2013 Members Share Posted June 7, 2013 Goose, I was referring to passing line level signal from the input XLR through to the link out, there is a switch that selects parallel or low pass out on this. Link to comment Share on other sites More sharing options...
Members agedhorse Posted June 7, 2013 Members Share Posted June 7, 2013 I have seen a fair amount of defective iec connectors. Does the power led go out under failure condition? Link to comment Share on other sites More sharing options...
Members djerickson Posted June 9, 2013 Author Members Share Posted June 9, 2013 Yes.....it goes completely dead....no signal light or power light on the front and it stops passing thesignal to the tops. The fact that it powered right back up when I switched power cables point to the cable as the problem, but with the same cable plugged into the Top it powered up and didn't skip a beat the rest of the night. Craig did say maybe the act of movine the cable from sub to top restored the faulty connection. I hate to have to start bringing my crossover to the gigs again but at least by using that instead of the subs crossover, when the sub dies it doesnt take the top on that side with it. Link to comment Share on other sites More sharing options...
Members agedhorse Posted June 9, 2013 Members Share Posted June 9, 2013 So we can rule out the audio part of the equation.I would first start with the power cable, ID if you run into this problem again. It could also be a defective connector or wire connection inside the speaker, but that's a warranty issue. Check for the simple things first. Link to comment Share on other sites More sharing options...
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